This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of this R21 project is to test the hypothesis that ASL can be used as a novel method to detect and quantify AV shunting in AVM or AVF, while simultaneously evaluating effects on brain perfusion. The first part of the proposal focuses on further development and optimization of the ASL perfusion MRI technique for use in this setting. In the second part of the proposal, patients with suspected AVM or AVF who are undergoing DSA will also be studied using the optimized ASL perfusion MRI technique in a pilot study to assess its accuracy. In the third part of the proposal, the information obtained in the pilot study will be further analyzed to determine whether AV shunting can be quantified, whether alterations in CBF related to an AVM or AVF can be detected, and whether changes in AV shunt or CBF can be detected in those patients undergoing surgical excision or embolization.